Updated

Police shot dead two Uighur men and wounded a third Monday on the streets of Urumqi, where tens of thousands of troops are stationed to restore calm a week after deadly ethnic riots raged in the western Chinese city.

Police said the three men attacked them when they tried to pull them off a fourth Uighur, whom they had attacked with knives and rods. A government official in Urumqi who described the attack would give only his surname, Fan.

Beijing has poured troops into Xinjiang over the past few days, imposing tight control on Urumqi and surrounding areas to impose order after ethnic violence that left more than 180 people dead and 1,680 wounded last week. Though many members of the Uighur minority have accused security forces of using heavy-handed tactics in the wake of the riots, Monday's shooting was the first time officials have said police opened fire.

"The police fired into the air as a warning, but that did not stop the attack. The police then shot them according to law," Fan said. He said the wounded man was taken to a hospital. His condition was not known.

Photos taken at the time show one policeman raising his rifle to strike a man. The man lay on the ground with blood on his right leg. Police formed a ring around him, pointing their guns up at surrounding buildings.

The shootings played out in front of frightened residents near one of the city's main Uighur neighborhoods.

One witness, Zhang Ming, a construction worker at a nearby building site, said he saw three men with knives come out of a mosque and attack a group of paramilitary police standing in a cluster along the road. Riot police then chased them, beat them and fired shots, he said. It was not immediately clear why Zhang's account differed from the police description. There were no Uighurs in the area who were willing to talk to reporters about the shooting.

A few hours later a large splotch of blood smudged the street. Squads of helmeted riot police took up positions on the road, which was closed to traffic.

In a sign of the sensitivities surrounding the unrest, the Bureau for Legal Affairs of Beijing has warned lawyers away from cases involving the Xinjiang violence, saying it is important to protect the country's unity.

While it did not expressly ban lawyers from taking on cases, the notice urged caution while answering inquiries about legal advice and representation.

Earlier Monday, security vehicles previously deployed on People's Square were no longer there but helmeted riot police remained in the area. Small groups of paramilitary police with riot shields stood guard on street corners and helicopters flew over the city.

The violence began when Uighurs (pronounced WEE-gers) who were protesting the deaths of Uighur factory workers in a brawl in southern China clashed with police in Urumqi (pronounced uh-ROOM-chi). Crowds scattered throughout the city, attacking ethnic Han Chinese and burning cars.

Government officials have yet to make public key details about what happened next, including how much force police used to restore order. In the following days, vigilante mobs of majority Han Chinese ran through the city with bricks, clubs and cleavers seeking revenge.

The government has said 137 Han Chinese and 46 Uighurs died, with one minority Hui Muslim also killed. Uighurs say they believe many more from their ethnic group died in the government crackdown. The death toll in China's worst ethnic violence in decades could rise as 74 of the more than 900 people still in hospitals have life-threatening wounds, the official Xinhua News Agency said.

Xinhua said police manned checkpoints and searched buses for any suspects involved in the violence, and people were ordered to carry identification for police checks when traveling in Urumqi.

It quoted the Urumqi Public Security Bureau as saying anyone without proper identification would be taken away to be interrogated.

The Uighurs, who number 9 million in Xinjiang, have complained about an influx of Han Chinese and government restrictions on their Muslim religion. They accuse the Han of discrimination and the Communist Party of trying to erase their language and culture.